The present disclosure relates to optical elements having on their surface, an antireflection structure for reducing reflection of incident light.
In recent years, various types of optical elements having an antireflection structure for reducing reflection of light on their surface have been suggested.
In one suggested antireflection structure, fine structure units (e.g., a fine structure having groove or ridge projections or recesses, a fine structure having cone, pyramid, or column projections or recesses, etc.) are formed on the surface of an optical member at a pitch equal to or smaller than the wavelength of incident light.
For example, Japanese Patent Publication No. 2006-053220 shows an optical element having an antireflection structure on a real or virtual curved surface. The antireflection structure includes fine structure units arranged at a pitch equal to or smaller than the wavelength of light whose reflection is to be reduced.